Feeding of magnetic sheet material



Sept. 1, 1953 A. FOWLER 2,650,824

FEEDING OF MAGNETIC SHEET MATERIAL Filed Nov. 26, 1949 4 Sheet s-Sheet 1 m gmm gyggg;

INVENTOR. Az A N05? FOh/A Fe A. FOWLER FEEDING OF MAGNETIC SHEET MATERIAL Sept. 1, 1953 4 Sheets-Sheet 2 Filed Nov. 26, 1949 INVENTOR. AzaxA/v z-ze FOA/LT? WSQN Sept. 1, 1953 A. FOWLER 2,650,824

I FEEDING OF MAGNETIC SHEET MATERIAL Filed Nov. 26, 1949 4 Sheets-Sheet K? 4 232 g, f 2% INVENTOR.

21.4 Z-XA N015? FOWLF? BY w AV V'OQA/FVEL Sept. 1, 1953 A. FOWLER FEEDING 0F MAGNETIC SHEET MATERIAL 4 Sheets-Sheet 4 Filed Nov. 26, 1949 Patented Sept. 1, 1953 FEEDING OF MAGNETIC SHEET MATERIAL Alexander Fowler, Brooklyn, N. Y., assignor to Hercules Electric & Mfg. Co., Inc., Brooklyn, N. Y., a corporation of New York Application November 26, 1949, Serial No. 129,662

24 Claims. 1

This invention relates to the feeding of sheet material, and more particularly to the automatic separation and feeding of single sheets in succession from a stack of ferromagnetic sheets.

Magnetized bodies of like polarity repel, and it has already been proposed to make use of this fact for the separation of the successive topmost sheets from a stack of sheet metal. The idea is applicable to any ferromagnetic material, but in present day commercial practice the common material for which it is suggested is ferrous metal. Prior attempts have been unsuccessful for various reasons, such as inability to produce a strong magnetic field within the sheets in proper direction, or because of variations in the thickness, permeability, or stiffness of the sheet material. The prior systems were not readily adjustable to sheets of different area or size, or of diiferent gauge, and were inherently slow and unreliable in operation.

The primary object of the present invention is to generally improve magnetic sheet separation and feeding apparatus. A more particular object is to produce a wide separation of the sheets magnetically, which will make it possible to feed the uppermost sheet from the stack without necessitating the use of auxiliary supporting means such as suction cups or other such mechanical means. A more particular object is to produce a magnetic flux field which extends longitudinally of the sheets, and preferably throughout the entire length of the sheets. From another viewpoint it may be said that an object of the invention is to use the stack of sheets itself as a massive core through which the magnetic flux field is passed, the flux returning in opposite direction outside the stack. This has the advantage of dispensing with the need for outside cores, and the more important advantage that the natural flux path diverges or fans out at the ends of the stack, thus facilitating the desired wide separation or fanning out of the sheets.

With these objects in view the apparatus includes a large induction coil having generally rectangular windings so dimensioned as to entirely surround the stack of sheets being operated on, the axis of said coil extending longitudinally of the sheets, that is, in the direction in which the sheets are to be fed from the stack.

A further object of the invention is to provide suitable means for feeding the topmost sheet from the stack. For this I provide a magnetic feed roller above the leading end of the sheet at such a height that when power is applied to the main induction coil the top sheet flies upward into contact with the feed roller. Appropriate switch means are provided so that the main induction coil is energized while the roller is stationary, and is de-energized while the roller is rotated. The de-energization of the induc tion coil frees the top sheet for feed movement, and releases the subjacent sheets, permitting them to fall back on the stack. In addition there is a saving of power.

A further object of the invention is to provide means for alternate energization of the main induction coil, and rotative drive of the feed roller. With this object in view the apparatus is preferably provided with a feeler so disposed as to be moved by the topmost sheet when that sheet is raised far enough to reach the feed roller. The feeler may take the form of a suitably positioned microswitch, and operation of the microswitch may start drive of the feed roller, as, for example, by engaging a magnetic clutch which is located between a constantly running motor and the feed roller. The microswitch also is used to de-energize the main induction coil. When the sheet has been fed out of the stack the feeler responds to the passage of the sheet and may be used to re-energize the main induction coil and to stop the drive of the feed roller.

If this is done too promptly the leading edge of the next sheet may be raised into engagement with the trailing edge of the preceding sheet, and thus cause trouble. In accordance with a further feature and object of the present invention this possibility is overcome in any of a number of ways, one being to include a time delay relay in the circuit, which delays re-energization of the main induction coil long enough to insure passage of the trailing edge of the preceding sheet. Another is to provide a second feeler and switch beyond the stack and the feed roller, and to so connect the switch in circuit with the first feeler switch that the main induction coil is not reenergized until the trailing edge of the preceding sheet passes the second as well as the first feeler switch.

A further object of the invention is to guard against the possibility of more than one sheet adhering to the feed roller. This object may be fulfilled in a number of different ways, some of which are described in the detailed specification. One is to energize an electro-magnetic feed roller with two different degrees of energization. The feed roller is first energized only limitedly in order to hold but one sheet, while the feed roller is stationary. It is energized much more strongly,

3 however, after the main induction coil is deenergized and while the feed roller is rotated, in order to guard against slippage at the feed roller. In some cases this arrangement may be further refined with the provision of three stages of energization of the feed roller, the first stage being strong enough to surely hold the topmost sheet even though it strike the roller somewhat forcibly with a tendency to rebound. In consequence the roller may possibly hold two sheets instead of one. The second stage of energization is the weakest stage, applied after the main induction coil has been de-energized, and is adequate to hold only one sheet under static conditions. The third stage is a strong energization of the feed roller, applied while the feed roller is rotated.

However, the object of insuring thefeeding of only a single sheet at a time may be fulfilled in wholly different fashion by energizing the main induction coil with a slowly growing current (or one tooth of a low speed saw-tooth wave). In such case the topmost sheet begins to separate ahead of the next subjacent sheet, and so on, and there is a relatively wide and individual separation of the sheets as the topmost sheet reaches -the feed roller. The feed 'roll'er may be uniformly strongly energized at all times, and may be made of permanently magnetic material. "when the topmost sheet reaches the feed roller the energization of the main induction coil is terinitiated, and the topmost sheet is promptly fed from the stack. This subject matter is not claimed herein, it being-claimed in my copending application Serial No. 226.656, filed May 16, 1951, which application is a continuation-impart of the present application.

When dealing with thin, light-weight sheets there may be 'atendency for the sheet to be pulled forward by the main induction coil when the coil is energized. This results from a solenoid action by the coil on the sheet when thecoil isdisposed near the forward end of the stack. Anobject of the present invention is to overcome this difficulty, which may be done'by the provision of a back induction coil whichis preferably disposed in symmetrical relation to the main induction coil, and in "the same electrical circuit for energization simultaneously therewith. Another method is to provide a hold-down foot which bears down on'a'nd holdsthe trailing'edge of the topmost sheet during 'ener'gizatidn of the main induction coil. 'Still another plan is to employ "only one main induction coil, but to locate the same "at 'thecenter of -thestack so that there is no tendency to pull thesheets either forward or backward.

To accomplish the foregoing general objects, and other more particular objects which will hereinafter appear, my invention resides 'in the sheet separating and feeding elements, and their relation one to another, as "arehe'reinafter more particularly described i'n'the following specification. Thespecificationis accompaniedby drawings inwhich:

Fig. 1 is a plan view of sheet separating and feeding apparatus embodying features of my invention;

Fig.2 is a section takenin elevation, approximately in the-plane of'the lin'e'2'2 of Fig. 1;

Fig. 3 is a schematic wiring diagram explanatory of one form of'the invention;

Fig.4 is a section similarto Fig. 2 schematically illustrating a modification; V

Fig. 5'isa similar section'showin'gstill another modification;

coil it and away from the stack It.

Fig. 6 is a schematic diagram explanatory of still another modification of the invention; and

Fig. '7 is explanatory of a current growth curve or saw-tooth wave used in connection with the form of the invention shown in Fig. 6.

Referring to the drawing, and more particularly to Figs. 1 and 2, the apparatus comprises a bed or table 12 for supporting a stack of sheets l4, and an induction coil !6 which extends entirely around the stack [4 and the table 42, and

which acts as a sheet separating means. The axis of the coil extends in the direction in which the sheets are to be-fed, which in this case is horizonta'lly, from left -.-to right. The apparatus further includes feed means generally designated 20 for feeding the uppermost sheet 22 through the The feed means ZU-preferably includes an electro-magnetic roller 24 capable of feeding sheet 22 with the latter disposed beneath the roller. The roller is preferably intermittently driven, as by means of a'magnetic clutch 26 disposed between the roller and a constantly rotating motor 28. The latter may rotate one or more sets of later feed rollers, indicated schematically at 25, through a drive 21.

The sheets may be stacked between guide plates 36, supported within side plates 32, preferably by means of adjusting screws 34, so that sheetso'f different'w'idth may be accommodated. The sheets are aligned at their forward edge by 'means'of front stops such as the posts '36, which are preferably made of non-magnetic material. The table 12, on the other hand, is preferably made of ferrous or magnetic material in order to repel and raise eventhe last sheet "of the stack.

If desired the table f 2 may be of the elevator type, that is, it maybe provided with suitable means to gradually raise "the same as the height of the stack is reduced, thus keeping the spacing between the top of the stack and the feed roller substantially 'constant. Mechanism for this .purpose is not shown, in order not to unduly complicate the "drawing. Such mechanism is already known, "an example being that disclosed in U. S. Patent 'No. 1,870,314, "issued to 'E. S. Lincoln on August 9, 1932.

'Before referring to the wiring diagram, attention is directed to the slip rings 33 (Fig. 1) and brushes '40 which supply magnetizing current to the coils 42 of the feejd'r'oller 24. Also the 'feeler 44'(Fig. 2) controlling'switc'h contacts 4 6. "When the top most sheet "22 reaches the feed-roller 24 the feeler is moved'from the broken'lineposition 44' 'to the solid line position 44, thus closing the normally open'contacts 46. It will be understood that the showing in Fig, 2 is merely schematic, and 'thatin practice a fully enclosed and sensitive microswitch'm'ay be used for the intended purpose. Moreover, other means to discriminate between the absence or presence of a'sheet may be-used.

Re'feren'ce is now madeto Fig. 3, which is a wiring diagram of one form of the invention. The 'main'indu'ction coil [6, the feed ro'ller'24, the magnetic clutch 26, the motor "28, and the feeder switch or microswitch 46, all correspond to the similarly "numbered .p'arts already referred to in Figs. 1 and'2. 'While n'ot-essential, it is preferred to energize the induction coil f5 and the feed roller 24 by means of direct current, and inasmuch as an alternating current supply is more commonly available, as -is indicated by lines I and "2 "at the left end or the diagram, rectifier means 48 is provided for the induction coil l6, and rectifier means 58 is provided 'for the feed roller 24. These are preferably of the full-wave .type as shown.

The table is stacked with metal sheets to proper height. A main power switch 52 controls the overall energization of the circuit, and is first closed. The feeler switch or microswitch 46 preferably operates through a relay indicated at 54. This is of the single pole double throw type, and is normally closed to the upper contact 56. To insure complete delivery of a preceding sheet out of the apparatus before re-energization of the main induction coil I6, a time delay relay 58 is provided. The coil 60 of this relay is energized through the upper or normally closed contact 56 of relay 54, thus closing the relay 58 and supplying power to the coil 62 of an'auxiliary relay 64. Relay 64 is merely a power relay to carry the power supply to rectifier 48 and main induction coil I6. Thus closing the main power switch 52 energizes the main induction coil I6, after a brief delay, say one second, occasioned by the time delay relay 58.

The operation of the bridge-type rectifier 48 is self-evident from the drawing. The variable resistor 66 is suitably adjusted to establish the desired energization of the main induction coil I6, and when once adjusted need not be varied so long as sheets of the same size, gauge, and material are being handled. The power return from the induction coil I6 is through conductor 68, rectifier 48, and conductor 10 to line 2 of the power supply.

Upon energization of the induction coil I6 the top sheet flies up to the feed roller 24, which is then stationary. As the sheet reaches the feed roller it closes the contacts of the microswitch 46 and so energizes its relay 54, thus closing the same to the lower contact 12, and opening the upper contact 56. This de-energizes the time delay relay 58, thus de-energizing its auxiliary or booster relay 64, which in turn de-energizes the main induction coil I6. The closing of the lower contact 12 of relay 54 energizes the coil 14 of a relay 16, and the coil 18 of a relay 80. It also supplies current through conductor 62 to rectifier 59 and thence through conductor 84 to the magnetizing coils of the feed roller .24. The return circuit is through conductor 86 and conductors 88 and 98 in parallel. Considering conductor 8B first, the circuit continues through adjustable resistor 92, rectifier 50, conductor 94, and conductor 96, back to line 2 of the input or supply source. The resistor 92 is so adjusted relative to the weight of the sheet being handled as to just hold the topmost sheet under static conditions.

The shunt or additional return path from conductor 86 is through conductor 96, adjustable resistor 98, the contacts of relay 80, conductor I00, conductor I62, the rectifier 50, and thence through conductors 94 and 96 to line 2. The adjustable resistor 98 provides a path in shunt with the adjustable resistor 92, and so strengthens the magnetization of the feed rollers 24. The magnetic attraction is made slightly greater than needed for static conditions, for the topmost sheet may hit the roller with some force and tend to rebound. Consequently the increased magnetic attraction of the roller may occasionally support two sheets instead of one. However, the remaining sheets fall because of thede-energization of the main induction coil l6.

The relay 80 is a time delay relay set for a brief interval, say one second, following which its contacts open, thereby opening the shunt resistor circuit through resistor 98. At this time the magnetization of the feed roller is solely through the resistor 92, and as previously explained, during this second period the magnetization of the feed roller is reduced to an amount just sufficient to hold only the topmost sheet under static conditions. In the event that the feed roller happens to be holding more than one sheet, the additional sheet or sheets are instantly dropped to the stack. After a suitable momentary interval, say one second at most, after relay 86 has opened the contacts I04 of the time delay relay I6 close. This supplies power directly from line I through contact I2, conductor I96, contacts I94, conductor I08, to coil IIO of a relay H2, and also to coil II4 of a relay H6. The resulting closing of the contacts of relay H2 serves to shunt the resistor 92 and thus to provide full power magnetization of the feed roller 24. In other words, the return path from the feed roller is through conductor 86, the contacts of relay II2, conductor I02, rectifier 50, and conductors 94 and 96 to line 2 of the power supply.

At the same time the energization of relay I I6 causes its contacts to close, thereby supplying power to the electrically operated clutch 26. The energization of the clutch is from line I through contacts "I2 of relay 54, conductor I06, contacts I04 of relay I6, conductor I08, and conductor M8 to the clutch 26. This may be a magnetic clutch, but that is not essential as any electrically--operated clutch will do. The return circuit from the clutch is through conductor I20, conductor I22, and conductor 96 to line 2 of the power supply.

Thus the sheet is fed forward, the feed roller being subjected to its most powerful magnetization and being set into rotation at the same time, all but the topmost sheet having been safely dropped back to the top of the stack.

When the trailing edge of the sheet moves past the feeler or microswitch 46 the microswitch opens, thus deenergizing the relay 54 and so restoring the parts to initial condition, that is, de-energizing the clutch 26 and so stopping the drive of the feed roller; reducing the energization of the feed roller to the relatively small or first stage energization; and again energizing the time delay relay 58. This provides adequate delay to insure passage of the trailing edge of the shet wholly out of the apparatus (under drive of later rollers such as 25 in Figs. 1 and 2) before the main induction coil I6 is re-ener-gized. The

- delay needed is quite small, say one second, at the end of which time the relay 58 closes, thus closing the auxiliary or booster relay, and so reenergizing the main induction coil I6, and thus causing a new sheet to fly upward to the feed roller and to engage the feeler or microswitch 46, all as was previously described.

It may be mentioned that the intervals of approximately one second each referred to above are on the liberal side, and contemplate moderate speed operation using ordinary relays. However, for high speed operation the intervals may be reduced, and electronic relays or vacuum tubes may be employed for extremely high speed operation.

It is preferred to use rectifiers (or a direct current supply) for the main induction coil because with direct current the amount of flux remains substantially constant per unit of area or per sheet, regardless of whether one is starting with .s-rtfnirstack. of sheets, or finishing withrthe, last '{ew.=sheets. .With alternatingcurrent there isa changeiin reluctancewhen the .size of the core is :nuhstantially changed, and .conserruently an :change current, and-in flux; density .inthe sheets. However, this assumesthata con- ;stant separating force is wantedwhich-is strictllyatrne only when an. elevatorl table isemployed. If the .-table a is stationary it necessary to raise the .top most sheet a .greater distance .near the chief theistack than ynear thebeginningand a greater separating force may he wanted, and in case the useofalternatingcurrent would have ithe advantage of .providing a greater sepamtm forcewhenthe stack is small than when the-stack islarge.

inithenase. of the feedroller. direct current zpreferredzbecause with direct-current the :feed roller-is moreefiicient; there is notendencytoiyibration. of the sheet in contact with 1 the iced roller; andthe, grip. of .thezteed roller. on: the sheet :isconstent, .with no tendency towardiintermittent slippage as the :feedroller isrotated. However, it is possible to use alternating current instead-e1: direct current if desired.

:Itshouldzbeunderstood that thearrangernent o.f*Fig.;3 may-besimpli-fied in other waysin. addir-tionr-to;the-elimination of the rectifierabridge. cirzAn exampleisthat theieedroller maybe magnetized :in .two stages instead of three. -.that;pnrpose.it is necessary merely toorrit the shunt resistor 9,8,andits control relay 8.0,.in which as thegreed :roller will be onlylimitedly magnetized when the resistor-,Blis in circuit... andwill be I trongly magnetized to avoid slippage during prorhie powersuppl-yto the main induction coil 46 while the main control switch :52 .is open, thus cuttingout all. of theotherparts-ofthe appa atus i mi ar ut e switch .32am. be. m ved -n lanual1y fromits nomially lower-position to the uppen position shown in dotted lines, thus'prOvidingpower supply for testing and suitably. adjusting the magnetization. of the feed rolleril, while therest pfthe apparatusis cutout of.-.circuit by opening the main control switch.,52.

However, switch I32 .may be left in its upper position, thus modifying the energization of the feed roller, so that it is energized andattracts and so'hel-ps lift the top sheet upward while the main-induction coil is energized to raise the-upper sheetstoward the ma gnetically energized feed roller. =Ihe-feed roller thenhas three instead of fqurcconditions, that'isyit has medium, low, and high energization, instead of zero, medium, .low and; high energization, as previouslyv described.

- LBemreJeaY-ing Fig. ;3 -attention is. called to normalluclosed microswitch 29. This guards against teed-of multiple sheets. If multiple sheets are -fed :jinsteaduof only-onesheet, the micro,-

switch islopched, ahdiheclutch 264s disengaged, thereby interrupting the feed .ofithesheelis. The-switch :29 maybe arranged for actuation by =multip1e sheets in various .ways. .One such may :15 shown -.schematically in :Fig. *2, reverting to Whichitwill be seen-thatsthe switch 28 is e.

microswitch the =feeler. of'whichbears against the top roll. in practice it really -.bears against a vertically-movable hearing-thereof. '1: more than one :sheet reaches .the roll t5 the .microswitch reeler sis-raised andfithezswitehiopened. Inlpractice theswitehzmay he arranged'to .work through a'relayv of adequate current carrying. capacity for the. clutch control current.

:In the apparatus shown in .Figs. 1 and 2 the maininduction coil .15 isdisposed near-theforward end-oi the stack. When dealing withthin,

light-weight sheets, .say no ;more than/.6 oz. .in

weight, then: will :he a tendency for the sheets to move sforward asthey are raised. Thiswill be. evident if ithe :main induction .coil .16 vis considered to be a solenoidccoilr t being evidentlltha-t thesheet will actas asolenoid plungerand thus tend-to move forward. :To avoid this the-coil 15 maybe disposed symmetrically or at the center- .lineof :theslack, instead of near the forward end. However, this-may introduce a difleulty in that t'he sheet may tend.totip.or balance in either. direction. Another tiny/co.solve. theproblem .is schematically shown in :Fig. .4, in vrhich itwill beseen. that in addition to: the first or-lmain induction coil [6, a second inductionlcoil lit-is providedythe latter 2oeing.-.clisposed-v neantheqhack endof the stack, and preferably symmetrically disposed with relation tozthecoil J5. Noseparate wiring diagram is shown for :this :modifioation of the inventionbecause coils as and I134 are energized de-energiudsimultaneously. For this purpose the coils may be/connected either in shunt. or:in. series. :Thus the-diagram of Fig. .3 is adequate, it :being kept inminditha-t-the coil lziithere .showniislto be replaced hytwo cells arranged either inshnntorin series. The .coil 1'3l will tendto cause therear end.l36,of thetopmost sheet 1-38 vto-rise at the same-time as the *forwardnend, .but that is.-notits purpose. :Coil 11-34 is'to'loe thoughtuof as .a'hold-backcoil, the purposeof which is :to guard against :ifOIWfi'Id movement. of the sheetzilflil. under the; influence of the coil 16. 'Whenrthesheet engages thezfeeler A4 and the magnetic teed roller s24 :hothcoils l6 and 134 .are de-energized, thus permitting rearend t3fizofisheet 5.138., as=well -as'the subje- .cent sheets,:.t0 fail-back to the stack,.the forward end ofthesheetheing retainedabythe feed roller 24.

Fig. =5 illustrates another modification in the provision of a normally raised rhold-dow-n foot "200 for use with .thin, light-weight sheets. Hold-down foot 12cc be urged downwardly by suitable means '202 responsive to electrical power, or compressed or anyother suitable source of power which .may be conveniently available. .If the pressure foot 121% is solenoid operated'the means; 282 twill. comprise. essentialls, a solenoid :coil connected either shunt or in series with the induction coil .45, thus holding back the topmost. sheet coincidentally Wlththe energizationof inductioncoil t6. 'When the 'feed roller- 21 .moves :the-sheet the main induction coil l6 is..deaenergized andsolenoid 2112 is de-energized along with it,'thus releasingthe sheet for forwardf-eed. 1f thepressure foot'lofl is. operated iby compressed air @the air supply to the air .cylinder is preferably controlled by a suitable solenoid operated air valve, the latter in turn being so connected in circuit with the main induction coil I6 as to make the pressure foot operative whenever the main induction coil is energized, and inoperative when it is not.

- It will be recalled that the wiring diagram of Fig. 3 included a time delay (the relay 58) to delay re-energization of the main induction coil until the trailing edge of a preceding sheet has safely left the magnetic feed. roller 24. This avoids any possibility of the next top sheet being caused to fly upward prematurely, in which case the forward portion of said sheet may strike the bottom of the trailing portion of the preceding sheet, thus holding it back both physically and magnetically, or, in the alternative, causing the second sheet to be prematurely pulled forward by the first sheet. This result may be accomplished by using e second feeler instead of a time delay relay, and such an arrangement is schematically shown in Fig. 5 in which it will be seen that most of the parts, including the main induction coil I6 and magnetic feed roller 232, correspond to those previously described. However, the first ieeler I46 closes contacts I42 when engaged by the topmost sheet I44, and a second feeler I46 is provided outside the stack, said feeler serving to close contacts I48 when engaged by a sheet I50 passing through feed rollers I52. This is described further as an incident to the description of Fig. 6 which follows.

Fig. 6 schematically illustrates another form of my invention. The main feature of this arrangement is that the induction coil 2I6 is energized by a gradually increasing current which starts at zero and rises to a desired value. Thus the current may follow an intermittent sawtooth wave such as that illustrated in Fig. '7. In Fig. '7 it will be seen that the current rises from the point 2I8 to a maximum at 220, whereupon it is out 01f and remains 01f until the point 222. The interval between points 220 and 222 corresponds to the time during which the sheet is fed away from the stack by the feed roller. When the main induction coil I6 is re-energized beginning at point 222 the current again increases to a maximum as indicated at 224 and is again out off.

If the induction coil is energized in this manner the topmost sheet tends to be raised from the next subjacent sheet before the latter is raised at all, whereupon both rise before the third sheet rises, so that the fanning out or divergence or separation of the sheets is maintained as the induction coil is further energized. In any event the topmost sheet alone reaches the feedroller, and the induction coil may then be de-energized without danger of the feed roller holding more than one sheet. Indeed, by promptly de-energizing the induction coil when the topmost sheet reaches the feed roller it is found that the feed roller may be left at full energization, and further that it may be kept under constant rotation. Thus the apparatus of Fig. 6 is more complicated than that previously described in introducing suitable means to apply a growth current or saw-tooth current to the induction coil, but is simplified in eliminating the time delay relays and adjustable resistors and electrically operated clutch for the feed roller.

Referring to Fig. 6, a main power switch 228 is closed to supply power from an ordinary source indicated by lines I and 2. This supplies power through conductors 228 and 236 to feed roller ill) 232, the return being through conductors 234 and 23:6 to line 2. The power supply to the induction coil 2I6 is varied by means of a suitable variable impedance 246. If the power supply is alternating current this may be either a conventional Variac or a rheostat. Variac is a trade name of the General Radio Company for a variable voltage transformer (disclosed in Patent 422,009,013). It is a device which increases or decreases voltage by mechanical rotation of a contact engaging the windings of a transformer. If the power supply is direct current the variable impedance would, of course, be a rheostat. The power supply to the Variac 240 is from line I through conductors 228, 230 and 242, the return being through conductors 244, 234, and 236 and back to line 2.

The Variac 246 is driven through a one-revolution clutch 246 and reduction gearing 241 by means of a motor 248 energized from the power line through conductors 256 and 252. Onerevolution clutch 246 is electrically operated, and is initially engaged because of a supply of power from line i through conductor 254, normally closed contacts 256 of relay 258, and a conductor 2613. The return is through a conductor 262 to line 2. The resulting rotation of the Variac causes a growth in output current from zero until the one-revolution clutch disengages. The power available in this way for the main induction coil 2&6 could grow to a value greater than needed to raise the first sheet into engagement with the feed roller, but the power supply is interrupted by suitable means as soon as the sheet reaches the feed roller. The mechanical rotation of the Variac is continued under drive of motor 248, and is terminated after one revolution by the operation of the one-revolution clutch, thus preparing the apparatus for the separation and delivery of the next sheet.

In the meantime the growing current is supplied from the Variac through conductor 264, the normally closed contacts 266 of relay 25B, and conductor 266 to the induction coil 2 I6, the retur being through conductor 210.

In the present apparatus the complete passage of a sheet is determined by the use of two feelers as shown in Fig. 5, instead of a single feeler combined with a time delay relay as shown in Fig. 2, although either arrangement might be used. The first and second feelers or microswitches are indicated at I40 and I46. The contacts are normally open. When the topmost sheet flies upward and reaches the feed roller it closes the switch I46, thus energizing relay coil 212 and so opening the contacts 266 and thereby interrupting the energization of the induction coil. This drops all sheets but the uppermost sheet, the latter being held by the fully magnetized feed roller, which may be constantly rotated and which promptly begins feeding the sheet out of the stack. In this case the feed roller may be permanently magnetized, as by making the same of Alnico or other highly magnetic material. However, as here shown it is magnetized electrically, with a constant current supply.

Energization of relay 258 opens the contacts 256 and thus de-energizes the electrically controlled clutch 246 so that when it disengages at the end of a single revolution it will not again engage unless and until the preceding sheet has been fed entirely out of the apparatus.

When the trailing edge of the sheet leaves the feeler I40 the relay coil 272 is not yet de-energized because of the action of the feeler I46, and thereacadaca.

fore the main induction coilis not yet re-energized. However; when the trailing. edge of the sheet leaves'the second feeler I46 the relaycoil 272 is-de-energized', the contacts 256-and .266 are again closed, and the induction coil is again energized to raise another sheet to the feed. roller.

It is believed that the construction. and operation; as well as the advantages-of my improved apparatus for separating andcfeeding sheets will be. apparent from the foregoing detailed descriptionthereof. It'will. also be apparent that while I have shown and described the invention in several preferred forms, changes may be made in the structuresdisclosed without departing from the scope-of the invention as sought to be defined in the following claims.

I claim:

1.- Apparatus for separating and successively feeding ferromagnetic sheets from a stack of sheets, said apparatus comprising a support for the stack of sheets, an induction coiL extending entirely around'thestack of sheets,- with the axis of the coil extending generally in the direction of the plane of the sheets and-generallyperpendicul'a'r tothe desired direction of separation oil the sheets, means to energize thecoil. in order to raise'andzseparate-the uppermost sheets of the stack, and. feed. means to receive and feed the uppermostsheet away from the coiland. stack.

2; Apparatus for separating and successively feeding ferrous sheetsfroma stack of sheets, said apparatus: comprising a support for the stack of sheets, an induction: coil extending entirely around the. stack: of 'sheets,1..with the. axis of the coil extending in the. direction: ofthe plane of the sheetsan'd' generally perpendicular to" the desired direction of separation of the sheets; means to energize the coilin order totraise and separate the uppermost sheetsiof 'thest'ack, and a: magnetic feedirollerto feedzithe uppermost sheetaway from the coil andista'ck.

3. Apparatus: for separating and successively feeding: ferromagnetic sheets from. a stack of sheets, said! apparatus comprising a support for the stack of sheets, an induction coil rextending entirel around the-stack. or sheets, a sheet feeding means disposed'near the'leadingend of the stack, drive means for intermittentlydriving the feed means, meanstd' energize the induction coil in order to raise and separate theuppermostsheet of the stack andxto: bring it to'rthe feed-means, and. appropriate switch means for the' induction coil interlocked. with the. drive'means whereby the induction coil isenergized while the feed means is inoperativeiand.isrde energized while-the feed means is operative:

4; Apparatus for separating and successively feeding ferrous sheets froma stack. ofsheetsysaid apparatus comprisinga support: for thestack of sheets, an induction coil: extending entirely around the stack of sheets, with the axis 'oi' the coil extending in the direction in which-"the sheets are to be fed, a magnetic'feed roller disposed over the leading end of the stack, drive means for intermittently driving. the' roll'er; means'to energize the coil in order to raise and separate the uppermost sheet of the stack and to bring it to the feed roller, and appropriate switch means for the induction coil interlocked with the-drive means whereby the induction coil is energized while the roller is stationary and is de -energized while the roller is rotated.

5. Apparatus for. separating and successively feeding ferromagnetic" sheets from a staclc of sheets, said apparatus comprising a'support for the stack of sheets, a maininducti'on winding extending entirely around the stack of sheets, amagnetic roller having a magnetizing coil, intermittently operabledrive means 1 for. intermi-tztently rotating the roller, means to energizev the main induction. winding in order to raise and separate theuppermost sheetof the stack and w bringit' to the roller, means for supplying current to said coil, means to energize the coils/to only a limited'extent sufiicient to hold the upper.- most" sheet when the feed roller is not. rotating, means to more strongl-yenergizethe coil in order to feed the sheet without appreciable slippage when the roller is rotated, and. appropriate switch 1 means-to. energize the main inductionw-inding when the'feed roller. is-stationary', and. to deenergize-the main induction winding when the feed roller is-rotating.-

6-. Apparatus for separating. and successively feeding ferrous sheets from a stack of sheets, said apparatus-comprising a supportfor the stack of'sheets, a main induction winding extending entirely, aroundvthe stack of sheets, with the axis of the winding extending; in the. direction in which the sheets are to be. fed, a magnetic roller having magnetizing coils distributed: therealong; intermittently operable drive means for intermittently rotating the roller, slip rings for suprplyingcurrentto said coils, means to energize the maininduction winding in order to raise and separate the uppermost sheet of the-stack and to -bring. it to the roller, means .to energizenthe coils:- toonly a limited: extent suflicient to hold the uppermost sheet whenthe feed; roller is not rotating, means to: more strongly energize the coils in order to feed thesheet-without appre ciable slippage when theroller is rotated; and appropriate switch means. to: energize the main induction winding. when; the. feed: roller isstationary, andzto d e-energize; the main'induction winding. when: the feedyroller is rotating.

7. Thecombinationv of: claim 3; in which a feeler isrdisposed above theistacl'c at'such. aheight that, it is. moved by uppermost sheet when the. uppermost sheet :has, beeniraisedxto: the; feed means, saidlfeeler serving to; operate thesaforesaid switch-means:

8. The combination of claim 5,.1'n which a feeler isrdisposed above therstack' at such a'height that it is movedby the uppermost sheet: when the. uppermost sheet has 'beenzraised: tozthe feed roller,- said feeler. serving to operate the aforesaidswitchmeans;

Qa-The combination-50f claim 3, in which a delayrelay 'is'disposed in the circuit to preventre energization of the induction coil until after the training edge of a preceding topmost" sheet has been safely fed beyond the leading edge of the stack.

10. The combination of claim 5; in which a delay relay is dispose'din the circuit to; prevent re-energization of the main induction. winding until after. the. trailing edge. of a precedingtopmostsheet has been-saielyfed. beyond the leading edgeof the stack.

11. Apparatus-as defined in claim. 3, in which there: are two' feelers, one of which is disposed over the stack and is responsive to thepresence of. a sheet; in engagement with the. feed: roller, and the other of which is disposed ahead of the stackandjs responsive to the feeding of a sheet fromzthe stack, and switches controlled by said feelers and'iso' arranged in the'circuit as to preventtre-energization of the induction-coil until after the trailing edge of a preceding topmost sheet has passed both feelers.

12. Apparatus as defined in claim 5, in which there are two feelers, one of which is disposed over the stack and is responsive to the presence of a sheet in engagement with the feed roller, and the other of which is disposed ahead of the stack and is responsive to the feeding of a sheet from the stack, and switches controlled by said feelers and so arranged in the circuit as to prevent re-energization of the main induction winding until after the trailing edge of a preceding topmost sheet has passed both feelers.

13. Apparatus for separating and successively feeding ferromagnetic sheets from a stack of sheets, said apparatus comprising a support for the stack of sheets, an induction coil extending entirely around the stack of sheets, with the axis of the coil extending generally in the direction in which the sheets are to be fed, means to energize the coil in order to raise and separate the uppermost sheets of the stack, feed means to receive the uppermost sheet when raised and to feed it away from the stack, and feeler means responsive to the thickness of the sheet material being fed away from the stack for interrupting operation of the feed means if more than one sheet is being fed.

14. Apparatus for separating and successively feeding ferromagnetic sheets from a stack of sheets, said apparatus comprising a support for the stack of sheets, an induction coil extending entirely around the stack of sheets, means to energize the coil in order to raise and separate the uppermost sheets of the stack, a sheet feeding means disposed near the leading end of the stack to receive the uppermost sheet when raised, drive means for intermittently driving the feed mans, appropriate switch means for the induction coil interlocked with the drive means whereb the induction coil is energized while the feed means is inoperative, and the induction coil is de-energized while the feed means is operative, and feeler means responsive to the thickness of the sheet material being fed from the stack for interrupting the operation of the drive means if more than one sheet is being fed.

15. Apparatus for separating and successively feeding ferromagnetic sheets from an upright stack of generally horizontal sheets, said apparatus comprising a support for the stack of sheets, an induction coil disposed in an upright plane and having each of its windings extending entirely around the stack of sheets, with the top of the coil higher than the top of the stack to provide substantial clearance therebetween, and with the axis of the coil extending generally horizontally in the direction in which the sheets are to be fed, means to energize the coil in order to raise and separate the uppermost sheets of the stack, and feed means to receive the uppermost sheet when raised and to feed it in a generally horizontal direction away from the coil and stack.

16. Apparatus for separating and successively feeding ferromagnetic sheets from an upright stack of generally horizontal sheets, said apparatus comprising a support for the stack of sheets, an induction coil disposed in an upright plane and having each of its windings extending entirely around the stacks of sheets, with the top of the coil higher than the top of the stack to provide substantial clearance therebetween, and with the axis of the coil extending generally horizontally in the direction in which the sheets are to be fed, means to energize the coil in order to raise and separate the uppermost sheets of the stack, and a magnetic feed roller having a horizontal axis extending across the direction of feed and disposed at a point higher than the stackbut lower than the top of the induction coil, said magnetic feed roller serving to receive the uppermost sheet when raised and to feed it in a generally horizontal direction away from the coil and stack.

17. Means for feeding a ferromagnetic sheet, said means including a magnetic sheet feed roller having a magnetizing coil, intermittently operable drive means for intermittently rotating the feed roller, a first supply circuit to energize the coil to only a limited extent, a second supply circuit to more strongly energize the coil, and appropriate automatic means so interconnecting the drive means and said supply circuitry that the coil is supplied by the first circuit when the feed roller is not driven by the drive means, and is supplied by the second circuit when the feed roller is driven by the drive means.

18. Means for feeding the uppermost sheet from a stack of ferrous sheets, said means including a magnetic sheet feed roller disposed above the stack and having magnetizing coils distributed therealong, means to bring the top sheet within the influence of the feed roller, intermittently operable drive means for intermittently rotating the feed roller, a first supply circuit to energize the coil to only a limited extent sunicient to hold the uppermost sheet when the feed roller is not rotating, a second supply circuit to more strongly energize the coils sumciently to grip and feed the sheet without appreciable slippage when the feed roller is rotating, and appropriate automatic means so interconnecting the drive means and said supply circuitry that the coil is supplied by the first circuit when the feed roller is not driven by the drive means, and is supplied by the second circuit when the feed roller is driven by the drive means.

19. Apparatus for separating ferromagnetic sheets from a stack of sheets, said apparatus comprising a support for the stack of sheets, an induction coil extending entirely around the stack of sheets, with the axis of the coil extending generally in the direction of the plane of the sheets and generally perpendicular to the desired direction of separation of the sheets, and means to energize the coil in order to raise and separate the uppermost sheets of the stack.

20. Apparatus for separating ferromagnetic sheets for removal from an upright stack of generally horizontal sheets, said apparatus comprising a support for the stack of sheets, an induction coil disposed in an upright plane and having each of its windings extending entirely around the stack of sheets, with the top of the coil higher than the top of the stack to provide substantial clearance therebetween, and with the axis of the coil extending generally horizontally in the direction in which the sheets are to be removed, and means to energize the coil in order to raise and separate the uppermost sheets of the stack.

21. Apparatus for separating ferromagnetic sheets from a stack of sheets, said apparatus comprising a support for the stack of sheets, an induction coil disposed with the axis of the coil extending generally in the direction of the plane of the sheets and generally perpendicular to the desired direction of separation of the sheets, said coil being so large in diametral dimension that the sheets may be moved through the induction coil in thedircctiomoi' theaxisxofthe coil, and siidcoihrbeingj disposedso close to the stack that the fielcbofi the" coilruns: through the: stack; with theezstaci acting'asacorefor thefieid and coil, and means to'r energize the. coil inorder to raise and: separatethe uppermost sheets of the stack. 7 22; Apparatus: for: separating ferromagnetic sheetsionremoval-from anuprig-ht stack of generally horizontal sheets, said apparatus; compxisingia' support for the stack ofsheets, an;induction coil disposed in an. upright plane with thewtopoi: the coil higher" than the; top of the to provide substantial difference in elevation therebetweemanda with the axis of the coil extending; generally horizontally"v in the: direction inwhicmthe sheets-= are'tobe removed, said being so 1arge:in diametral dimension that thexs heets-maye beemovecl through the coir-inthe dircctionof the axisofthe coil, andsaid coilbe ing ,disposed near enough to the stackso that the fiel'dmf theucoil runs through'the stack, with the stack! actingasza c'ore'for the field-andrthecoil; :mdimeansto'energize the'coil in order to raise and separate the uppermost sheets ofthe-stack'.

23; Apparatus for" separatingand successively feeding; ferromagnetic sheets from a stack of sheets;:.said" apparatus comprising a support for the stack; of. sheets; anuinductioncoil' disposed withthe'axis of the coi-l extenchng generally in the; direction. of the plane" of the: sheets and generallyperpendi'cular to the'diesireclrdirection of sepamtion' oi= the sheetsysaid coilbei-ng'so' large inidiametricrdimension that the sheets-may be puiledlthrougii thEliIIEl'flCtiOIli coil in'the direction ofithesaxissofithe coil, and said coil being"dis-- posedzso: cieseto: thev stack that the of the coilirunseth rough the "stack, wriththe: stack acting as a coxeior'ithe field1 andieoi1-,.means to energize thmcotl inorden to raise and separate the upp er'- mostsheets oiithestack; and'ieed'meansrtareceive and feedrthe uizperi mostisheet away from the coil andistack.

214-.v Apparatus for: separating and-successively feeding ferromagneticv sheets from an upright stackof generally horizontal sheets, said apparatuscompri'sing a. support-for the stack o-f-sheets, an induction coihdisposed-in an upright. plane with thewtopof thecoil higher than the top ot the stack to provide substantial difierenee in elevation-therebetween and'with the axis of; the coil extending generally horizontally in thezdirection in which the sheets areto befed, said: coil being so large" in diametrio d-i-mensi'on'that' the sheets: may; be pulled through the coi'i in' the direction of: the axis ofi the: coil, and said coil beingdispose'd'near enough to the stack so that the field oi the-coil'runs through the stack. and the stack acts as a. core" for? that field. and the coil, means to energize the coil in order to raise and separate theuppermost sheets of the stack, and feed means to: receive'the uppermost sheet when raised and to:- feed it in a generally 'horizontal direction away from the coil and stack.

ALEXANDER FOVILER.

ReferencesCited-in thefile. of this patent UNITEDSTATES PATENTS Number Name Date Re. 15,858 Bedell June 10, 1924 963,170 Parker July 5, 1910 1,442,718 Free Jan, 16, 1923 1,444,999 Bennett et' a1. Feb. 13,- 1923 1,870,314 Lincoln Aug. 9, 1932 2,197,817 Theiss Apr. 23, 1940 2,374,174 Buccicone Apr. 24, 1945 24741141 Chatterton June 21, 1949 2,527,911 Buccicone Oct. 31, 1950 FOREIGN PATENTS Niimber Country Date 175,083 Great Britain Feb. 16, 1922 

